1. Field of the Invention
The present invention relates to a digital data transmission apparatus, a digital data reception apparatus, a digital broadcast reception apparatus, a digital data transmission method, a digital data reception method, a digital broadcast reception method, a computer program, and a computer readable recording medium. In particular, the present invention is suitable for time division multiplexing of an MPEG2 stream and arbitrary data.
2. Description of the Related Art
A TS (Transport Stream) of MPEG2 includes reference clock information called PCR (Program Clock Reference) (SCR (System Clock reference) in a PS (Program Stream) of MPEG2), and program synchronization information concerning decoding time and presentation time called DTS (Decode Time Stamp) and PTS (Presentation Time Stamp). In order to attain synchronization intended by the transmission side, the reception side needs to correct the system clock on the basis of the PCR.
In correction of the system clock, there are two kinds. In first correction, a clock value on the transmission side indicated by the PCR is set on the reception side. In second correction, a difference between PCR arrival time intended by the transmission side and actual PCR arrival time is detected as PCR fluctuation and a system clock frequency is increased or decreased in a predetermined range. Herein, the former cited operation of setting the clock value (PCR counter value) on the transmission side to the clock value on the reception side is referred to as “PCR reference time correction,” whereas the latter cited PCR fluctuation correction is referred to as “PCR fluctuation correction.”
A demand for transmission of a TS of MPEG2 (hereafter referred to as MPEG2 TS) concurrently with other data such as of JPEG data, DV (Digital Video) data or the like input from an external input apparatus after reception of the MPEG2 TS is conceivable in the case where a transmission path is present between an input management section for managing an input and a signal processing section for conducting data processing. As described above, however, the MPEG2 TS is subject to the PCR reference time correction and the PCR fluctuation correction according to the arrival time of the PCR. Therefore, it is not easy to conduct time division multiplexing on the MPEG2 TS and arbitrary data. Herein, “arbitrary data” refers to image data, voice data, and control system data.
Typically, when transferring an MPEG2 TS from a certain processing section to another processing section, the MPEG2 TS occupies the transmission path, and concurrent transfer of the MPEG2 TS and other data is not conducted. Or if the transmission path is shared by the MPEG2 TS and other data, program synchronization using the PCR is not conducted and the program synchronization information is discarded. According to a typical method for reflecting synchronization information such as the PCR as well while transmitting JPEG and DV information in concurrent with a MPEG2 TS in the conventional technique, the MPEG2 TS is temporarily demultiplexed, and the demultiplexed MPEG2 TS and the JPEG and DV information are multiplexed again into a MPEG2 TS. This method has a problem that both the quantity of processing and the memory in use increase.
Japanese Patent Application Laid-Open (JP-A) No. 2000-183841 discloses a method for multiplexing a plurality of TSs into one TS without conducting demultiplexing. However, multiplexing of a MPEG2 TS and arbitrary data is not mentioned, and the method cannot be applied to arbitrary data.